Device for monitoring an air supply flow or a volumetric air flow

ABSTRACT

The invention relates to a device for monitoring an air supply flow or a volumetric air flow, in particular for ventilators which can also be applied for extremely low flow speeds and/or throughput rates. The aim of the invention is to produce a device cheaply and simply with essentially wear-free components which reacts to changes in the flow speed and/or the throughput rate without a time delay. Said aim is achieved, whereby the device comprises an approach flow device, the position of which may be altered relative to a mounting, against a retaining force F M  and which may be impinged by the air flow for monitoring to generate a change in the position thereof. Furthermore, magnetic devices for the generation of a magnetic field dependent on the position of the approach flow device, detection means for recording the magnetic field and measuring means for generation of a measured signal dependent on the magnetic field are provided. The magnetic field forms at least a part of the retaining force F M .

The invention relates to a device for monitoring an air supply flow or avolumetric air flow according to the precharacterizing clause of claim1.

Apparatus that contains electrical and/or electronic components, e.g.switch cabinets, must as a rule be air-conditioned or activelyventilated. Such forced ventilation serves to circulate the air in theswitch cabinet and move it past the components in a targeted manner,because not only the thermal emission from the installed components butalso the heat exchange with the surroundings could produce a climatewithin the cabinet that would put the functionality of its contents atrisk. To ensure continuous ventilation, what is needed in addition tothe actual air-flow generating mechanism is a supplementary control unitthat monitors the ventilating operation by checking the air supply flowor volumetric air flow.

At present devices for monitoring an air supply flow or a volumetric airflow are often supplied in a purely electronic construction. As a rule,these operate according to the thermodynamic principle. That is, ameasurement sensor is heated by an internal source so as to create atemperature difference between the sensor and the medium flowing pastit. Because energy is extracted from the sensor by the flowing medium,the state of flow of the medium can be derived therefrom. Devices ofthis kind demand a very complex electronic system, which is extremelyexpensive and can function smoothly only in dependence on certaininfluential variables. For instance, specially designed sensors areneeded, e.g. sensors with relatively large mass, when the flow to berecorded is quite small, because the sensors customarily used do notrespond in this case. As a consequence, because of the interaction ofthe additional mass and the slight flow, it is necessary to allow forprolonged response times. Therefore if the system operation is disturbedby insufficient ventilation, it will take a long time before this can benoticed.

Other kinds of devices for monitoring the air supply flow or thevolumetric flow comprise mechanically operating components, for instancecomponents that are displaced when air flows against them, so that theirchange of position provides information about the medium to bemonitored. In order to move these approach-flow detectors back to theoriginal position other mechanical components, e.g. springs, are needed.Additional components of this kind, however, increase the susceptibilityof the monitoring device to damage, e.g. on account of greater wear andtear. In particular, it is difficult to design the spring arrangement soas to ensure that the air current can be monitored despite a very widerange of flow velocities and/or throughput rates.

The objective of the present invention is to construct a device formonitoring the air supply flow and/or the volumetric air flow in thesimplest manner that will ensure high reliability.

This objective is achieved by a device according to claim 1.

In particular, the objective is achieved by a device for monitoring anair supply flow or volumetric air flow that comprises an approach-flowcomponent, the position of which with respect to a holder can be changedagainst a retaining force F_(M); the air flow to be monitored canimpinge against the approach-flow component, in order to produce achange in the latter's position. Magnet components are provided togenerate a magnetic field that depends on the position of theapproach-flow component, as also are detection means for recording themagnetic field and measuring means to generate a measurement signal thatdepends on the magnetic field. The magnetic field forms at least a partof the retaining force F_(M).

It is a substantial point of the invention that the approach-flowcomponent, the position of which is changed by the impinging air flow,is subject to a restoring force when the flow velocity decreases and/orthe throughput rate becomes lower, owing to the magnetic retaining forceF_(M). This restoring force returns the approach-flow component to itsinitial position, with no need for a separate repositioning mechanism tobe provided.

Thus in a first preferred embodiment of the device it is provided thatthe magnet components comprise a permanent magnet. This brings aboutorderly operation of the device without the need for a separate supplyof current, as would have been the case, e.g., for an electromagnet. Thedevice can be manufactured simply and cost-effectively and is nearlymaintenance-free. Findamentally, however, an electromagnet can alsofulfill the desired function.

Furthermore, as one of the preferred embodiments it is provided that thepermanent magnet is mounted on the approach flow component, so thathere, too, a simple and economical manufacture is ensured. Mounting thepermanent magnet on the approach-flow component achieves a directcoupling of magnetic field and switching action, with no need foradditional components.

Another possible implementation of the device consists in mounting thepermanent magnet on the holder and a magnetic, in particularferromagnetic element on the approach-flow component. This protects themagnet on one hand, while on the other hand enabling a preciselyspecified quantity associated with the magnetic element to be used forextremely sensitive adjustment of the device to flow velocities and/orthroughput rates.

In another advantageous embodiment of the device in accordance with theinvention, the approach-flow component comprises a flap rotatablysuspended in such a way that the air flow generates a moment of torqueon the flap, about its axis of suspension. Such a flap can be mounted bysimple means.

One solution in accordance with the invention provides that the approachflow component is equipped with at least one counterweight or similarmass-compensation element, so that it can be installed independently ofposition and gravity. Hence the device for monitoring an air supply flowor volumetric air flow can be mounted at any desired place and in anydesired orientation. This is especially advantageous when there is notmuch room for it to be installed, or the places to be used are difficultto access.

In a special embodiment the mass compensation is implemented by aneccentric mounting of the approach-flow component. The advantageousaspect here is that no additional components need to be incorporated toserve for mass compensation, so that a simple and economical manufactureof the device is possible. Because of the savings in mass, furthermore,the approach-flow component can respond more rapidly to low flowvelocities and/or throughput rates.

Alternatively or in addition, the counterweight can comprise at leastparts of the magnet components. Here, again, the number of additionalcomponents needed as mass-compensation elements can thus be reduced, soas to ensure simple and economical manufacture of the device. Thebehavior of the approach-flow component in response to low flowvelocities and/or throughput rates is likewise positively influenced.

Furthermore, as one of the preferred embodiments, it is provided thatthe measurement means comprise a reed contact, which is disposed in areed-contact switch. The advantage here is that the reed contactresponds to a magnetic field and therefore switches without mechanicalactuation. Therefore the switch and the approach-flow component need notbe connected to one another by leads, so that the device can beconstructed in a compact, simple manner.

The reed-contact switch, in another embodiment, is disposed so that in amagnetic field it generates at least part of the retaining force F_(M).Magnetic, in particular ferromagnetic elements, which are immanent inreed-contact switches, in themselves enable an attraction between switchand permanent magnet. This, again, allows a simple, compact and henceeconomical construction of the device, because no additional componentsare needed.

A preferred implementation of the device consists in providingadjustment means such that the retaining force F_(M) can be adjusted.This results in optimization of the device to the most diverse flowvelocities and/or throughput rates. In particular, limiting values canbe set for flow velocities and/or throughput rates, as required. This isadvantageous, for instance, when the spaces to be ventilated—e.g.,switching cabinets containing heat-generating apparatus—have differentdimensions and hence need different ventilation.

In a special embodiment of the device in accordance with the inventionan adjustment of the retaining force F_(M) is enabled by additionalmagnetic, in particular-ferromagnetic elements that can be introducedinto the magnetic field. Consequently limiting values for flowvelocities and/or throughput rates can be specified in the simplestpossible way, so as to guarantee extremely reliable operation of thedevice.

Alternatively or additionally, the retaining force F_(M) can be adjustedby positioning the reed-contact switch at different distances from thepermanent magnet to form the adjustment apparatus. The differentialspacing can, for example, be produced by simply shifting the permanentmagnet on the approach-flow component. Thus no other elements are neededto adjust the retaining force F_(M).

Another embodiment in accordance with the invention provides foralteration of an effective surface of the approach-flow component. Thespecial advantage in this case is that the response sensitivity of thedevice can be varied.

In a special embodiment the housing is constructed in such a way thatthe effective surface of the approach-flow component can be changed byway of the housing, which serves as its holder. This can be achieved,for instance, by way of openings in the housing. Hence this makes itextremely economical to produce a series of such devices.

In another advantageous embodiment the approach-flow component ismounted in such a way that it is in its resting state when the permanentmagnet is kept, by the retaining force F_(M), at the shortest distancefrom the reed-contact switch. This ensures that the device can beconfigured as simply as possible.

In a preferred implementation of the device, the holder for themeasurement means is designed to serve as a housing. As a result, themeasurement means are protected from external influences and hence canoperate reliably and precisely.

Other embodiments of the invention will be apparent from the subordinateclaims.

In the following the invention is explained with reference to exemplaryembodiments, the description of which is assisted by the attacheddrawings, wherein

FIG. 1 shows a longitudinal section of the device in accordance with theinvention;

FIG. 2 a shows a section along the line II-II in FIG. 1;

FIG. 2 b is an enlargement of the section along the line II-II in FIG.1.

The longitudinal section in FIG. 1 represents a special embodiment ofthe device 1 in accordance with the invention, for monitoring an airsupply flow or volumetric air flow 2. Here an approach flow element isprovided in the form of a pivotally mounted flap 3 to which is attacheda permanent magnet 4 in a magnet holder 5. The flap 3 is suspended in apivot bearing 6 and therefore is rotationally deflected by the air flow2. The permanent magnet 4 is positioned on the axis of symmetry,perpendicular to the axis of rotation, at the edge of the flap 3.

Because the flap 3 is provided with at least parts of the magneticelements—in this case the permanent magnet 4—the flap 3 must be providedwith at least one counterweight or similar mass-compensating element, sothat it can be installed without regard to the force of gravity or toits orientation. Hence in the present drawing the flap 3 is disposedeccentrically, so that in this way a mass compensation on the basis ofdifferent-sized areas is ensured. In this exemplary embodiment aneffective area section 7 is provided as compensatory surface—that is,the larger portion of the area of the flap 3, which interacts with theair flow 2. The permanent magnet 4 is disposed on a smaller area section8.

The present drawing shows a reed-contact switch 9, which comprises reedcontacts 10. The reed-contact switch 9 is preferably potted, inparticular in order to protect the glass body. The current is suppliedby way of leads 12. The switch 9 in this case is arranged so that theinteraction between the permanent magnet 4 and the reed contacts 10 inthe magnetic field generates at least part of the retaining force F_(M).In addition, the contact holders 11, which as a rule are made of aniron-nickel alloy, can interact with the magnetic field of the permanentmagnet 4.

The exemplary embodiment comprises adjustment means that allow theretaining force F_(M) to be adjusted. As can be seen in FIG. 1, theinitial setting of the retaining force F_(M) is accomplished extremelysimply by selecting a particular distance d, between the reed-contactswitch 9 and the permanent magnet 4, that is appropriate for an intendeddetection behavior of the device 1.

FIGS. 2 a and 2 b show a section along the line II-II in FIG. 1. FIG. 2b is an enlargement of FIG. 2 a, to make some details clearer. Thepivotally mounted flap 3, the permanent magnet 4, the magnet holder 5and the reed-contact switch 9 are shown here again, in plan view. Thesmaller area portion 8, the permanent magnet 4 in the magnet holder 5and the reed-contact switch 9 are disposed in the interior of the closedhousing part 13 a, and accordingly are protected thereby. The device 1also comprises both inflow and outflow openings 14, by way of which theair flow 2 is diverted through the device 1.

As shown in FIGS. 2 a and 2 b, the device 1 comprises between themovable flap 3 and a lateral housing part 13 c a sealing gap 15, becausethe lateral housing part 13 c on the side facing the flap 3 is shapedwith a radius r₂=r₁+x, according to which the radius r₂ is larger by avalue x than a radius r₁ of the circle described by the effective areaportion 7 of the flap 3 as it makes its pivotal movement. Now, if alengthwise housing part 13 b, as shown in FIG. 2 b, is set into anopening 14 of the housing, the result is a smaller opening 14 a andreduced flow through the sealing gap 15, so that the pressure drops andthe device becomes less sensitive.

The operating principle of the arrangement is as follows:

An air flow 2 passes through the inflow opening 14 and reaches theeffective area portion 7 of the rotatably mounted flap 3. Because of thepivot bearing 6 in which the flap 3 is suspended—rather like arocker—the air flow 2, in this exemplary embodiment, exerts a moment oftorque on the flap 3, tending to rotate it about its axis of suspension.That is, the yielding movement of the flap 3, induced by the air flow 2,is a pivotal movement. The device 1 is constructed such that both ablowing and a sucking air flow 2 can be detected. For this purpose theflap 3 can be deflected in a rightward as well as a leftward directionof rotation. Then the inflow and outflow openings 14 operate inversely.In the resting state the flap 3 is kept in its resting position becauseof the interaction of the magnetic field of the permanent magnet 4 withthe magnetic material in the reed-contact switch 9. The reed contact 10is closed by the magnetic field of the permanent magnet 4 and, ifdesired, can induce a warning signal. If a blowing or sucking air flow 2is present, it must now deflect the flap 3 against the magneticallyacting retaining force F_(M). When this occurs, the permanent magnet 4is moved away from the reed contact 10, so that the latter opens onaccount of the weakening magnetic field. The interruption of the circuitthen signals that the ventilation is in order. If the flow velocityand/or throughput rate of the air flow 2 decreases, the flap 3 willagain approach its resting position, because the retaining force F_(M)acts as a restoring force when the flap 3 is in a deflected state. Asmentioned above, no additional restoring mechanism is needed to returnthe flap 3 to its initial position; the interaction between the magneticmaterial in the reed-contact switch 9 and the magnetic field of thepermanent magnet 4 suffices to move the flap 3 back. As soon as the flap3 again approaches the reed contact 10, the latter closes and can, ifdesired, again trigger a warning mechanism. The concept of the“approach” of the flap 3 to the reed contact 10 should be regardeddifferently, depending on the desired detection behavior of the device10. The alternatives for construction and mode of action of the device 1that are explained below will provide further information in thisregard.

In general it is possible to construct the approach-flow component notas a rotatably mounted flap 3 but rather as a plate, the position ofwhich could be changed by a translational movement. Then the platewould, for instance, be guided on rails or be held by several magnetsand pushed or sucked along by an air flow 2.

The permanent magnet 4 can in principle also be replaced by anelectromagnet, which would likewise be fixed within the magnet holder 5.The leads that supply the electromagnet with current could then, forinstance, run through the interior of the pivot bearing.

When the permanent magnet 4 is used, it could also be fixedly attachedto a holder associated with the housing 13. The magnet holder 5 wouldthen serve to carry a supplementary magnetic, in particularferromagnetic element, which in this case would complete the magnetcomponent.

As described above, the flap 3 must be provided with at least onecounterweight or similar mass-compensation element, in order tocompensate for additional masses, such as that of the permanent magnet4. This mass compensation can also be implemented by measures other thanthe eccentric arrangement of the flap 3. If the mounting of the flap 3is concentric, its two areas could be made of different materials, sothat the difference in their densities would amount to a masscompensation. Cutting out some of the flap material or attachingadditional elements would also have a compensatory effect.

FIGS. 1, 2 a and 2 b show an exemplary embodiment in which the retainingforce F_(M) is initially adjusted by selecting a distance d betweenreed-contact switch 9 and permanent magnet 4 that is appropriate for anintended detection behavior of the device 1. In the example presentedhere the distance d is constant, but it is entirely possible for it tobe made alterable. To that end, the housing 13 would have to beconstructed such that the flap 3 could be variably inserted into thehousing 13. By enlarging the distance d of the permanent magnet 4 fromthe reed-contact switch 9, for instance, the retaining force F_(M) wouldbe overcome even by low flow velocities and/or throughput rates, thusenabling a change in the position of the flap 3. The opening 14 couldalso be altered by a covering, either in the form of part of the housing13 that is attached thereto by permanent connection of the materials oras a removable piece. Here the phrase “permanent connection of thematerials” is meant to denote connections formed by classical methodssuch as welding or the use of adhesives, as well as every other means ofconnecting things, in particular including the construction of anintegral housing 13. It would now be possible to regulate the pressureor suction of the air flow 2, and hence the response sensitivity of thedevice 1, in dependence on the sizes of the opening 14 a and the sealinggap 15. Additional magnetic, in particular ferromagnetic elements wouldallow further adjustment of the retaining force F_(M) by altering theinteraction between the magnetic element and the magnetic field of thepermanent magnet 4. Preferably the magnetic element would be disposed inthe reed-contact switch 9, in order to reinforce the magnetic action ofthe contacts 10. Variation of the magnetic field induced by theelectromagnet also presents another possible means of adjusting theretaining force F_(M).

In the present exemplary embodiment, shown in FIGS. 1, 2 a and 2 b, theleakage at the sealing gap 15 is kept as small as possible byconfiguring the lateral housing part 13 c so that its shape approximatesthe path along which the effective surface portion 7 of the flap 3 movesas it is deflected. Additional elastomer sealing lips or brushes couldrestrict the leakage still further, but in some circumstances wouldincrease the friction. The solution that is best in any given casedepends on the situations for which the device 1 is to be employed. Itwould be entirely possible to make the sealing gap wider intentionally,so that the deflection of the flap 3 would begin only at a particularminimal flow velocity and/or throughput rate of the air flow 2. Then ifthe flow velocity and/or throughput rate is below that limit, because ofthe intentional leakage not enough impact pressure will build up tocause the flap 3 to be deflected.

At this juncture it should be pointed out that all of the partsdescribed above, individually or in any combination, in particular thedetails shown in the drawings, are claimed as essential to theinvention. Modifications thereof are familiar to a person skilled in theart.

LIST OF REFERENCE NUMERALS

-   1 Device for monitoring an air supply flow or a volumetric air flow-   2 Air flow-   3 Flap-   4 Permanent magnet-   5 Magnet holder-   6 Pivot bearing-   7 Effective area portion-   8 Smaller area portion-   9 Reed-contact switch-   10 Reed contacts-   11 Contact holders-   12 Leads-   13 Housing-   13 a Closed-off part of housing-   13 b Lengthwise part of housing-   13 c Lateral part of housing-   14 Openings-   14 a Reduced opening-   d Distance-   r₁ Radius 1-   r₂ Radius 2

1. Device for monitoring an air supply flow or a volumetric air flow,comprising an approach-flow component adapted to be struck by an airflow that is to be monitored so as to produce a change in its position;a holder on which the approach-flow component, is mounted but relativeto which the approach-flow component can change its position against aretaining force F_(M); magnet components adapted to produce a magneticfield dependent on the position of the approach-flow component, theforce of said magnetic field forming at least part of the retainingforce F_(M); detection means adapted to detect the magnetic field; andmeasurement means adapted to generate a measurement signal that dependson the strength of the magnetic field.
 2. Device according to claim 1,wherein the magnet components comprise a permanent magnet.
 3. Deviceaccording to claim 2, wherein the permanent magnet is attached to theapproach-flow component.
 4. Device according to claim 2, wherein thepermanent magnet is fixedly attached to the holder and a magneticelement is attached to the approach-flow component.
 5. Device accordingto claim 1, wherein the approach-flow component comprises a flaprotatably suspended in such a way that the air flow exerts a moment oftorque on the flap, about its axis of suspension.
 6. Device according toclaim 1, wherein the approach-flow component is provided with at leastone counterweight so that it can be installed regardless of the force ofgravity and of its position.
 7. Device according to claim 6, wherein theapproach-flow component is eccentrically seated and a larger areaportion of the approach-flow component is provided as saidcounterweight.
 8. Device according to claim 6, wherein the counterweightcomprises at least parts of the magnet components.
 9. Device accordingto claim 1, wherein the measurement means comprises a reed contact,which is disposed in a reed-contact switch.
 10. Device according toclaim 9, wherein the reed-contact switch is disposed in such a way thatin the magnetic field it generates at least part of the retaining forceF_(M).
 11. Device according to claim 1, wherein adjustment means areprovided so that the retaining force F_(M) can be adjusted.
 12. Deviceaccording to claim 11, wherein the adjustment means comprise additionalmagnetic elements that can be brought into the magnetic field. 13.Device according to claim 2, wherein the position of the reed-contactswitch can be adjusted with respect to its distance from the permanentmagnet in order to provide an adjustment means whereby the retainingforce F_(M) can be adjusted.
 14. Device according to claim 11, whereinan effective area of the approach-flow component can be altered. 15.Device according to claim 14, wherein the housing is constructed in sucha way that the effective area of the approach-flow component can bealtered by constructing the holder as a housing.
 16. Device according toclaim 9, wherein the approach-flow component is mounted in such a waythat it is in a resting state when the magnet component is retained bythe retaining force F_(M) at the shortest distance to the reed-contactswitch.
 17. Device according to claim 1, wherein the holder isconstructed as a housing and the measurement means are disposed in thehousing.